1. Technical Field
The present invention relates to a rotatable electrical plug, and more particularly, to a rotatable electrical plug having an effectively reduced size.
2. Description of Related Art
With development of the science and technologies, various domestic appliance products have become indispensable to the life, what accompanies this is massive demands for electric power. In order to supply electric power for these domestic appliance products, an electrical plug must be used to connect a receptacle to receive the power. Sometimes, the electrical plug must be inserted in different directions in order to adapt to the position of the receptacle, and this is likely to cause excessive rotation or bending of electrical wires and thus increases the probability of damaging the electrical wires.
U.S. Pat. No. 5,399,093 discloses a rotatable electrical plug, which has a rotary electrical connection device comprising a first set of conductors and a second set of conductors. The first set of conductors is contacted and connected with conductors of corresponding electrical wires, and the second set of conductors is contacted and connected with conductors of corresponding plug pins. Therefore, after the first set of conductors and the second set of conductors are electrically connected, the electrical wires and the plug pins can be electrically connected. Furthermore, when the electrical plug has two plug pins, the first set of conductors has two conductive pieces, and the two conductive pieces are both an annular metal sheet and must both surround a center of a housing of the electrical plug while being electrically isolated from each other. One of the conductive pieces is disposed as an inner ring, and the other of the conductive pieces is disposed as an outer ring.
If such a design is applied to an electrical plug having three plug pins, then the first set of conductors has three conductive pieces, with one of the conductive pieces being disposed as an innermost ring and the other two of the conductive pieces being disposed as a middle ring and an outermost ring. Because the number of the conductive pieces varies with the number of the plug pins and the conductive pieces are transversely arranged in the housing of the electrical plug in sequence, a too large transverse dimension of the electrical plug will be caused. When there is a need to apply the electrical plug of such a design to a receptacle sequence having more than two receptacles, a too large space will be occupied and adjacent receptacles will be blocked due to the too large transverse dimension of the electrical plug, which causes inconvenience in use.
U.S. Pat. No. 7,566,223 discloses an electrical connector having three tubular conductors which are vertically stacked in sequence. Although the aforesaid problem of the too large transverse dimension of the electrical plug is eliminated, there is a shortcoming that a longitudinal dimension of the electrical plug is too large, which is likely to cause inconvenience in storage. Moreover, when there is a need to plug this electrical plug into a receptacle behind a piece of furniture, the electrical plug may fail to extend to the behind of the furniture due to the too large thickness.
Referring to FIG. 1, there is shown a perspective exploded view of a rotatable electrical plug of the prior art. China Utility Model No. 2,253,877 discloses a rotatable electrical plug 10, which uses two tabular conductors and one tubular conductor 13 simultaneously to reduce both the longitudinal dimension and the transverse dimension of the electrical plug 10. Moreover, the electrical plug 10 further uses a U-shaped metal annulus 11 and a U-shaped metal annulus 12 in place of the two tabular conductors to reduce the transverse dimension of the electrical plug 10. Although the transverse dimension of the electrical plug 10 can be slightly reduced by using the U-shaped metal annulus 11 and the U-shaped metal annulus 12 simultaneously, a spring (not shown) is still used thereunder to push the U-shaped metal annulus 11 and the U-shaped metal annulus 12 upwards to electrically connect with electrode ends 16 of plug pins 15. The upward elastic force will add to the difficulty in packaging of an upper housing 17 and a lower housing 18. Accordingly, it is desirable to develop a rotatable electrical plug that allows to be packaged more conveniently and has a reduced volume.